1. Field of the Disclosure
The present disclosure relates to an organic anti-reflective coating polymer suitable for use in ultrafine pattern formation during fabrication of a semiconductor device, an organic anti-reflective coating composition comprising the coating polymer, and a method for forming a photoresist pattern with the coating composition.
2. Description of the Related Art
In recent years, as semiconductor devices have become smaller in size and more densely integrated, photoresist patterns have necessarily become finer. It is thus necessary to make the linewidths of photoresist patterns finer. To prevent disruption of photoresist patterns arising from the aspect ratio of the photoresist patterns, the photoresist patterns must be formed to a predetermined thickness or less, taking the linewidths of the photoresist patterns into consideration. For example, when it is intended to form a sub-70 nm fine pattern, the linewidths of a photoresist pattern must not be larger than 70 nm. Accordingly, the photoresist pattern must be formed to a thickness of a maximum of 150 nm. If the photoresist pattern has a thickness larger than 150 nm, disruption of the photoresist pattern takes place due to the aspect ratio of the photoresist pattern.
Organic anti-reflective coatings are formed under photoresist patterns in order to absorb light emitted from an exposure light source so as to prevent damage to the photoresist pattern due to diffuse reflection or standing waves, etc. from an underlayer, which is to be etched and patterned by the photoresist pattern, upon exposure to light. As the thickness of the photoresist pattern becomes smaller, the thickness of the organic anti-reflective coating formed under the photoresist pattern must also become smaller.
Under such circumstances, since currently used organic anti-reflective coatings typically have a low refractive index of 1.5 to 1.65, organic anti-reflective coatings having a small thickness cannot exhibit desired light absorption properties in response to exposure light sources, and as a result, they cannot sufficiently prevent damage to photoresist patterns due to diffuse reflection, etc. from the underlayer upon exposure to light.
For these reasons, although a photoresist pattern has a small thickness, an organic anti-reflective coating having a thickness of at least 30 nm is currently formed under the photoresist pattern. As a result, the organic anti-reflective coating is not completely removed during etching and removing the organic anti-reflective coating and underlayer, using the photoresist pattern as a mask, and consequently insufficient patterning of the underlayer occurs.
In view of the above-mentioned problems, there is a continuous need to develop an organic anti-reflective coating material which has a high refractive index (e.g., 1.70 or higher) so as to allow an organic anti-reflective coating to exhibit desired light absorption properties in response to an exposure light source when the organic anti-reflective coating is formed to a small thickness under a photoresist pattern, thereby preventing damage to the photoresist pattern due to diffused and reflected light, etc. from an underlayer upon exposure to light.